Methods and apparatus for fixing sheet-like materials to a target tissue

ABSTRACT

A device for attaching a sheet-like implant to a target tissue. The device includes a fastener push rod including a first portion, a second portion and a force limiting mechanism operably coupled between the first portion and the second portion. A fastener is carried by the second portion of the fastener push rod. The force limiting mechanism transmits longitudinal movement of the first portion to the second portion while the forces applied to the fastener by the fastener push rod are less than a predetermined value such that longitudinal movement of the first portion of the fastener push rod causes substantially equivalent longitudinal movement of the second portion. The force limiting mechanism allows relative longitudinal motion between the first and second portions while the forces applied to the fastener are equal to or greater than the predetermined value such that the application of undue forces to the fastener is prevented.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/397,573, filed on Feb. 15, 2012, which claims priority to U.S.Provisional Application No. 61/443,180 filed on Feb. 15, 2011, thedisclosures of each incorporated herein by reference.

FIELD

The present invention relates generally to orthopedic medicine andsurgery. More particularly, the present invention relates to methods andapparatus for delivery and fixation of sheet-like materials, such as fortreating articulating joints.

BACKGROUND

The glenohumeral joint of the shoulder is found where the head of thehumerus mates with a shallow depression in the scapula. This shallowdepression is known as the glenoid fossa. Six muscles extend between thehumerus and scapula and actuate the glenohumeral joint. These sixmuscles include the deltoid, the teres major, and the four rotator cuffmuscles. As disclosed by Ball et al. in U.S. Patent Publication No. US2008/0188936 A1 and as illustrated in FIG. 1 the rotator cuff musclesare a complex of four muscles. These four muscles are the supraspinatus,the infraspinatus, the subscapularis, and the teres minor. The centeringand stabilizing roles played by the rotator cuff muscles are critical tothe proper function of the shoulder. The rotator cuff muscles provide awide variety of moments to rotate the humerus and to oppose unwantedcomponents of the deltoid and pectoralis muscle forces.

The four muscles of the rotator cuff arise from the scapula 12. Thedistal tendons of the rotator cuff muscles splay out and interdigitateto form a common continuous insertion on the humerus 14. Thesubscapularis 16 arises from the anterior aspect of the scapula 12 andattaches over much of the lesser tuberosity of the humerous. Thesupraspinatus muscle 18 arises from the supraspinatus fossa of theposterior scapula, passes beneath the acromion and the acromioclavicularjoint, and attaches to the superior aspect of the greater tuberosity 11.The infraspinatus muscle 13 arises from the infraspinous fossa of theposterior scapula and attaches to the posterolateral aspect of thegreater tuberosity 11. The teres minor 15 arises from the lower lateralaspect of the scapula 12 and attaches to the lower aspect of the greatertuberosity 11.

The mechanics of the rotator cuff muscles 10 are complex. The rotatorcuff muscles 10 rotate the humerus 14 with respect to the scapula 12,compress the humeral head 17 into the glenoid fossa providing a criticalstabilizing mechanism to the shoulder (known as concavity compression),and provide muscular balance. The supraspinatus and infraspinatusprovide 45 percent of abduction and 90 percent of external rotationstrength. The supraspinatus and deltoid muscles are equally responsiblefor producing torque about the shoulder joint in the functional planesof motion.

The rotator cuff muscles 10 are critical elements of this shouldermuscle balance equation. The human shoulder has no fixed axis. In aspecified position, activation of a muscle creates a unique set ofrotational moments. For example, the anterior deltoid can exert momentsin forward elevation, internal rotation, and cross-body movement. Ifforward elevation is to occur without rotation, the cross-body andinternal rotation moments of this muscle must be neutralized by othermuscles, such as the posterior deltoid and infraspinatus. The timing andmagnitude of these balancing muscle effects must be preciselycoordinated to avoid unwanted directions of humeral motion. Thus thesimplified view of muscles as isolated motors, or as members of forcecouples must give way to an understanding that all shoulder musclesfunction together in a precisely coordinated way—opposing musclescanceling out undesired elements leaving only the net torque necessaryto produce the desired action. Injury to any of these soft tissues cangreatly inhibit ranges and types of motion of the arm.

With its complexity, range of motion and extensive use, a fairly commonsoft tissue injury is damage to the rotator cuff or rotator cufftendons. Damage to the rotator cuff is a potentially serious medicalcondition that may occur during hyperextension, from an acute traumatictear or from overuse of the joint. With its critical role in abduction,rotational strength and torque production, the most common injuryassociated with the rotator cuff region is a strain or tear involvingthe supraspinatus tendon. A tear in the supraspinitus tendon 19 isschematically depicted in FIG. 2. A tear at the insertion site of thetendon with the humerus, may result in the detachment of the tendon fromthe bone. This detachment may be partial or full, depending upon theseverity of the injury. Additionally, the strain or tear can occurwithin the tendon itself. Injuries to the supraspinatus tendon 19 andrecognized modalities for treatment are defined by the type and degreeof tear. The first type of tear is a full thickness tear as alsodepicted in FIG. 2, which as the term indicates is a tear that extendsthrough the thickness of the supraspinatus tendon regardless of whetherit is completely tom laterally. The second type of tear is a partialthickness tear which is further classified based on how much of thethickness is tom, whether it is greater or less than 50% of thethickness.

The accepted treatment for a full thickness tear or a partial thicknesstear greater than 50% includes reconnecting the tom tendon via sutures.For the partial thickness tears greater than 50%, the tear is completedto a full thickness tear by cutting the tendon prior to reconnection. Incontrast to the treatment of a full thickness tear or a partialthickness tear of greater than 50%, the treatment for a partialthickness tear less than 50% usually involves physical cessation fromuse of the tendon, i.e., rest. Specific exercises can also be prescribedto strengthen and loosen the shoulder area. In many instances, theshoulder does not heal and the partial thickness tear can be the sourceof chronic pain and stiffness. Further, the pain and stiffness may causerestricted use of the limb which tends to result in further degenerationor atrophy in the shoulder. Surgical intervention may be required for apartial thickness tear of less than 50%, however, current treatmentinterventions do not include repair of the tendon, rather the surgicalprocedure is directed to arthroscopic removal of bone to relieve pointsof impingement or create a larger tunnel between the tendon and bonethat is believed to be causing tendon damage. As part of the treatment,degenerated tendon may also be removed using a debridement procedure inwhich tendon material is ablated. Again, the tendon partial tear is notrepaired. Several authors have reported satisfactory early postoperative results from these procedures, but over time recurrentsymptoms have been noted. In the event of recurrent symptoms, many timesa patient will “live with the pain”. This may result in less use of thearm and shoulder which further causes degeneration of the tendon and maylead to more extensive damage. A tendon repair would then need to bedone in a later procedure if the prescribed treatment for partial tearwas unsuccessful in relieving pain and stiffness or over time the tearpropagated through injury or degeneration to a full thickness tear or apartial thickness tear greater than 50% with attendant pain anddebilitation. A subsequent later procedure would include the moredrastic procedure of completing the tear to full thickness and suturingthe ends of the tendon back together. This procedure requires extensiverehabilitation, has relatively high failure rates and subjects thepatient who first presented and was treated with a partial thicknesstear less than 50% to a second surgical procedure.

As described above, adequate treatments do not currently exist forrepairing a partial thickness tear of less than 50% in the supraspinatustendon. Current procedures attempt to alleviate impingement or make roomfor movement of the tendon to prevent further damage and relievediscomfort but do not repair or strengthen the tendon. Use of the stilldamaged tendon can lead to further damage or injury. Prior damage mayresult in degeneration that requires a second more drastic procedure torepair the tendon. Further, if the prior procedure was only partiallysuccessful in relieving pain and discomfort, a response may be to usethe shoulder less which leads to degeneration and increased likelihoodof further injury along with the need for more drastic surgery. There isa large need for surgical techniques and systems to treat partialthickness tears of less than 50% and prevent future tendon damage bystrengthening or repairing the native tendon having the partialthickness tear.

SUMMARY OF THE DISCLOSURE

The disclosure is directed to devices for attaching a sheet-like implantto a target tissue. One embodiment includes a fastener push rodincluding a first portion, a second portion and a force limitingmechanism operably coupled between the first portion and the secondportion. A fastener is carried by the second portion of the fastenerpush rod. An actuator assembly coupled to the first portion of thefastener push rod is provided. The actuator assembly is capable ofcreating longitudinal movement of the first portion. The force limitingmechanism transmits longitudinal movement of the first portion to thesecond portion while the forces applied to the fastener by the fastenerpush rod are less than a predetermined value such that longitudinalmovement of the first portion of the fastener push rod causessubstantially equivalent longitudinal movement of the second portion.The force limiting mechanism allows relative longitudinal motion betweenthe first portion and the second portion while the forces applied to thefastener are equal to or greater than the predetermined value such thatthe application of undue forces to the fastener is prevented.

Another embodiment includes a pronged sheath. The pronged sheath definesa lumen. The pronged sheath includes at least a pair of prongs extendingdistally beyond a distal end of the lumen such that the prongs formpilot holes when a distal portion of the pronged sheath is pressedagainst the target tissue. A fastener push rod extends into the lumendefined by the pronged sheath. The fastener push rod includes a firstportion, a second portion and a force limiting mechanism operablycoupled between the first portion and the second portion. A pair ofstakes are disposed at a distal end of the second portion of thefastener push rod. The pair of stakes carries a fastener. An actuatorassembly is coupled to the first portion of the fastener push rod andcapable of creating longitudinal movement of the first portion of thefastener push rod relative to the pronged sheath. The force limitingmechanism transmits longitudinal movement of the first portion to thesecond portion while the forces applied to the fastener by the fastenerpush rod are less than a predetermined value such that longitudinalmovement of the first portion of the fastener push rod causessubstantially equivalent longitudinal movement of the second portion.The force limiting mechanism allowing relative longitudinal motionbetween the first portion and the second portion while the forcesapplied to the fastener are equal to or greater than the predeterminedvalue such that the application of undue forces to the fastener isprevented. In some embodiments, the fastener comprises a staple and eachstake has a distal portion and a proximal portion with each distalportion being dimensioned to extend into a passage defined by thestaple. Each proximal stake portion has a width larger than a width ofeach distal portion so that a shoulder of each proximal portion contactsa proximal surface of the staple to apply pushing forces thereto.

In some exemplary embodiments, the force limiting mechanism comprises aconstant force spring. A first end of the constant force spring may becoupled to the first portion of the fastener push rod and a second endof the constant force spring may be coupled to the second portion of thefastener push rod.

In some exemplary embodiments, the first portion of the fastener pushrod includes a first tubular member, the second portion of the fastenerpush rod includes a second tubular member, and a portion of one tubularmember is slidingly received in a lumen defined by the other tubularmember such that the first tubular member and the second tubular membercan translate relative to each other. For instance, the first portion ofthe fastener push rod may include a first tubular member, the secondportion of the fastener push rod may include a second tubular member,and a portion of the first tubular member may be slidingly received in alumen defined by the second tubular member such that the first tubularmember and the second tubular member can translate relative to eachother. In some exemplary embodiments, the second tubular member definesa slot and the first tubular member carries a pin that is slidinglyreceived in the slot such that relative rotation between the firsttubular member and the second tubular member is prevented. The forcelimiting mechanism may include a constant force spring having a firstend coupled to the first tubular member and a second end coupled to thesecond tubular member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified perspective view of the human rotator cuff andassociated anatomical structure;

FIG. 2 is a schematic depiction of a full thickness tear in thesupraspinatus tendon of the rotator cuff of FIG. 1;

FIG. 3 is a stylized anterior view of a patient with a shoulder ofpatient being shown in cross-section for purposes of illustration;

FIG. 4 is a stylized anterior view of a shoulder including a humerus anda scapula. The head of the humerus is shown mating with the glenoidfossa of the scapula at a glenohumeral joint and a sheet-like materialis fixed to the tendon;

FIG. 5 is a stylized perspective view illustrating an exemplaryprocedure for treating a shoulder of a patient;

FIG. 6 is a stylized perspective view of a shoulder including asupraspinatus having a distal tendon with a sheet-like material fixedthereto. A proximal end of the supraspinatus is fixed to the scapula andthe distal tendon of the supraspinatus is fixed to the humerus;

FIG. 7A, FIG. 7B, and FIG. 7C are multiple plan views illustrating anexemplary staple in accordance with the present detailed description;

FIG. 8 is a perspective view further illustrating the staple shown inthe previous Figure;

FIG. 9 is a perspective view showing a staple push rod that may be usedin conjunction with the staple shown in the previous Figure;

FIG. 10A and FIG. 10B illustrate multiple plan views of an exemplaryfixation tool in accordance with the present detailed description;

FIG. 11A is a further enlarged partial cross-sectional view of a distalportion of the fixation tool shaft shown in the previous Figure;

FIG. 11B is an additional partial cross-sectional view showing a staplecarried by a staple push rod and a fixation tool shaft disposed aboutthe staple push rod;

FIG. 12A through FIG. 12C are a sequence of plan views illustrating anexemplary method and apparatus in accordance with the present detaileddescription;

FIG. 13A, FIG. 13B, FIG. 13C and FIG. 13D are multiview projectionsillustrating a fixation tool shaft shown in the previous figures;

FIG. 14 is an enlarged axial view of the fixation tool shaft shown inthe previous Figure;

FIG. 15 is an additional enlarged axial view of the fixation tool shaftshown in the previous Figure;

FIG. 16 is an exploded isometric view of an exemplary fixation tool inaccordance with the detailed description;

FIG. 17 is a perspective view showing an illustrative fixation toolassembly with overlying shaft removed in accordance with this detaileddescription;

FIG. 18A and FIG. 18B are plan views further illustrating the operationof the fixation tool assembly shown in the previous figure also withoverlying shaft removed;

FIG. 19 is a perspective view showing an illustrative fixation toolassembly in accordance with this detailed description with overlyingshaft removed; and;

FIG. 20A and FIG. 20B are plan views further illustrating the operationof the fixation tool assembly shown in the previous figure also withoverlying shaft removed.

DETAILED DESCRIPTION

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

As used herein, the term “tissue” refers to soft tissue, such as atendon, and/or bone tissue, depending on the context in which it isused.

FIG. 3 is a stylized anterior view of a patient 20. For purposes ofillustration, a shoulder 22 of patient 20 is shown in cross-section inFIG. 3. Shoulder 22 includes a humerus 14 and a scapula 12. In FIG. 3, ahead 24 of humerus 14 can be seen mating with a glenoid fossa of scapula12 at a glenohumeral joint. With reference to FIG. 3, it will beappreciated that the glenoid fossa comprises a shallow depression inscapula 12. The movement of humerus 14 relative to scapula 12 iscontrolled by a number of muscles including: the deltoid, thesupraspinatus, the infraspinatus, the subscapularis, and the teresminor. For purposes of illustration, only the supraspinatus 26 is shownin FIG. 3.

With reference to FIG. 3, it will be appreciated that a distal tendon 28of the supraspinatus 26 meets humerus 14 at an insertion point. Scapula12 of shoulder 22 includes an acromium 32. In FIG. 3, a subacromialbursa 34 is shown extending between acromium 32 of scapula 12 and head24 of humerus 14. In FIG. 3, subacromial bursa 34 is shown overlayingsupraspinatus 26. Subacromial bursa 34 is one of the hundreds of bursaefound the human body. Each bursa comprises a fluid filled sac. Thepresence of these bursae in the body reduces friction between bodilytissues. Injury and/or infection of the bursa can cause it to becomeinflamed. This condition is sometimes referred to as bursitis.

The exemplary methods and apparatus described herein may be used to fixtendon repair implants to various target tissues. For example, a tendonrepair implant may be fixed to one or more tendons associated with anarticulating joint, such as the glenohumeral joint. The tendons to betreated may be tom, partially tom, have internal micro-tears, be untom,and/or be thinned due to age, injury or overuse. Applicants believe thatthe methods and apparatus of the present application and related devicesmay provide very beneficial therapeutic effect on a patient experiencingjoint pain believed to be caused by partial thickness tears and/orinternal microtears. By applying a tendon repair implant early before afull tear or other injury develops, the implant may cause the tendon tothicken and/or at least partially repair itself, thereby avoiding moreextensive joint damage, pain, and the need for more extensive jointrepair surgery.

FIG. 4 is a stylized anterior view of a shoulder 22 including a humerus14 and a scapula 12. In FIG. 4, a head 24 of humerus 14 is shown matingwith a glenoid fossa of scapula 12 at a glenohumeral joint. Asupraspinatus 26 is also shown in FIG. 4. This muscle (along withothers) control the movement of humerus 14 relative to scapula 12. Adistal tendon 28 of supraspinatus 26 meets humerus 14 at an insertionpoint 30.

In the embodiment of FIG. 4, distal tendon 28 includes a first damagedportion 36. A number of loose tendon fibers 40 in first damaged portion36 are visible in FIG. 4. First damaged portion 36 includes a first tear42 extending partially through distal tendon 28. First tear 42 maytherefore be referred to as a partial thickness tear. With reference toFIG. 4, it will be appreciated that first tear 42 begins on the side ofdistal tendon 28 facing the subacromial bursa (shown in the previousFigure) and ends midway through distal tendon 28. Accordingly, firsttear 42 may be referred to as a bursal side tear.

With reference to FIG. 4, it will be appreciated that distal tendon 28includes a second damaged portion 38 located near insertion point 30. Inthe embodiment of FIG. 4, second damaged portion 38 of distal tendon 28has become frayed and a number of loose tendon fibers 40 are visible inFIG. 4. Second damaged portion 38 of distal tendon 28 includes secondtear 44. With reference to FIG. 4, it will be appreciated that secondtear 44 begins on the side of distal tendon 28 facing the humerus 14.Accordingly, second damaged portion 38 may be referred to as anarticular side tear.

In the embodiment of FIG. 4, a sheet-like implant 50 has been placedover the bursal side of distal tendon 28. With reference to FIG. 4, itwill be appreciated that sheet-like implant 50 extends over insertionpoint 30, first tear 42 and second tear 44. Some useful methods inaccordance with this detailed description may include placing a tendonrepair implant on the bursal side of a tendon regardless of whether thetears being treated are on the bursal side, articular side or within thetendon. In some cases the exact location and nature of the tears beingtreated may be unknown. A tendon repair implant may be applied to thebursal side of a tendon to treat shoulder pain that is most likelycaused by one or more partial thickness tears in the tendon. In theembodiment of FIG. 4, sheet-like implant 50 is fixed to distal tendon 28and to humerus 14 by a plurality of staples 100 as described herein indetail.

FIG. 5 is a stylized perspective view illustrating an exemplaryprocedure for treating a shoulder 22 of a patient 20. The procedureillustrated in FIG. 5 may include, for example, fixing tendon repairimplants to one or more tendons of shoulder 22. The tendons treated maybe tom, partially tom, have internal micro-tears, be untom, and/or bethinned due to age, injury or overuse.

Shoulder 22 of FIG. 5 has been inflated to create a cavity therein. Inthe exemplary embodiment of FIG. 5A, a fluid supply 52 is pumping acontinuous flow of saline into the cavity. This flow of saline exits thecavity via a fluid drain 54. A camera 56 provides images from inside thecavity. The images provided by camera 56 may be viewed on a display 58.

Camera 56 may be used to visually inspect the tendons of shoulder 22 fordamage. A tendon repair implant in accordance with this disclosure maybe fixed to a bursal surface of the tendon regardless of whether thereare visible signs of tendon damage. Applicants believe that the methodsand apparatus of the present application and related devices may providevery beneficial therapeutic effect on a patient experiencing joint painbelieved to be caused by internal microtears, but having no clear signsof tendon tears. By applying a tendon repair implant early before a fulltear or other injury develops, the implant may cause the tendon tothicken and/or at least partially repair itself, thereby avoiding moreextensive joint damage, pain, and the need for more extensive jointrepair surgery.

A delivery system 60 can be seen extending from shoulder 22 in FIG. 5.Delivery system 60 comprises a sheath that is fixed to a handle. Thesheath defines a lumen and a distal opening fluidly communicating withthe lumen. In the embodiment of FIG. 5, the distal opening of the sheathhas been placed in fluid communication with the cavity created inshoulder 22.

A tendon repair implant is at least partially disposed in the lumendefined by the sheath of delivery system 60. Delivery system 60 can beused to place the tendon repair implant inside shoulder 22. Deliverysystem 60 can also be used to hold the tendon repair implant against thetendon. In some embodiments, the tendon repair implant is folded into acompact configuration when inside the lumen of the sheath. When this isthe case, delivery system 60 may be used to unfold the tendon repairimplant into an expanded shape.

The tendon repair implant may be fixed to the tendon while it is heldagainst the tendon by delivery system 60. Various attachment elementsmay be used to fix the tendon repair implant to the tendon. Examples ofattachment elements that may be suitable in some applications includesutures, tissue anchors, bone anchors, and staples. In the exemplaryembodiment of FIG. 5, the shaft of a fixation tool 70 is shown extendinginto shoulder 22. In one exemplary embodiment, fixation tool 70 iscapable of fixing the tendon repair implant to the tendon with one ormore staples while the tendon repair implant is held against the tendonby delivery system 60.

FIG. 6 is a stylized perspective view of a shoulder 22 including asupraspinatus 26 having a distal tendon 28. With reference to FIG. 6, itwill be appreciated that a tendon repair implant 50 has been fixed to asurface of distal tendon 28. Tendon repair implant 50 may comprise, forexample, various sheet-like structures without deviating from the spiritand scope of the present detailed description. In some usefulembodiments, the sheet-like structure may comprise a plurality offibers. The fibers may be interlinked with one another. When this is thecase, the sheet-like structure may comprise a plurality of aperturescomprising the interstitial spaces between fibers. Various processes maybe used to interlink the fibers with one another. Examples of processesthat may be suitable in some applications including weaving, knitting,and braiding. In some embodiment, the sheet-like structure may comprisea laminate including multiple layers of film with each layer of filmdefining a plurality of micro-machined or formed holes. The sheet-likestructure can comprise collagen material having a porous structure suchas reconstituted bovine collagen. The sheet-like structure of the tendonrepair implant may also comprise a plurality of electro-spun nanofiberfilaments forming a composite sheet. Additionally, the sheet-likestructure may comprise a synthetic sponge material that defines aplurality of pores. The sheet-like structure may also comprise areticulated foam material. Reticulated foam materials that may besuitable in some applications are available from Biomerix Corporation ofFreemont, Calif. which identifies these materials using the trademarkBIOMATERIAL™.

Various attachment elements may be used to fix tendon repair implant 50to distal tendon 28 without deviating from the spirit and scope of thisdetailed description. Examples of attachment elements that may besuitable in some applications include sutures, tissue anchors, boneanchors, and staples. In the exemplary embodiment of FIG. 6, a pluralityof staples 100 are fixing tendon repair implant 50 to distal tendon 28.In some exemplary methods, a plurality of staples 100 may be appliedusing a fixation tool. The fixation tool may then be withdrawn from thebody of the patient. Distal tendon 28 meets humerus 14 at an insertionpoint 30. With reference to FIG. 6, it will be appreciated thatsheet-like implant 50 extends over insertion point 30. Tendon repairimplant may be applied to distal tendon 28, for example, using theprocedure illustrated in the previous Figure.

FIG. 7A, FIG. 7B, and FIG. 7C are multiple plan views illustrating anexemplary staple 100 in accordance with the present detaileddescription. FIG. 7A, FIG. 7B, and FIG. 7C may be collectively referredto as FIG. 7. It is customary to refer to multi-view projections usingterms such as front view, top view, and side view. In accordance withthis convention, FIG. 7A may be referred to as a front view of staple100, FIG. 7B may be referred to as a side view of staple 100, and FIG.7C may be referred to as a bottom view of staple 100. The terms topview, side view, and bottom view are used herein as a convenient methodfor differentiating between the views shown in FIG. 7. It will beappreciated that the staple shown in FIG. 7 may assume variousorientations without deviating from the spirit and scope of thisdetailed description. Accordingly, the terms top view, side view, andbottom view should not be interpreted to limit the scope of theinvention recited in the attached claims. A proximal direction isillustrated with an arrow P in FIG. 7. A distal direction is illustratedwith a second arrow Din FIG. 7.

Staple 100 comprises a first arm 102A, a second arm 102B, and a bridge104 extending from the proximal end of first arm 102A to the proximalend of second arm 102B. The distal end of first arm 102A abuts theproximal end of a first fluke 106A. Similarly, the distal end of secondarm 102B abuts the proximal end of a second fluke 106B. In FIG. 7, firstfluke 106A and second fluke 106B are shown extending distally from firstarm 102A and second arm 102B, respectively. With reference to FIG. 7, itwill be appreciated that first fluke 106A has a lateral extent that islarger than a lateral extent of first arm 102A. First fluke 106A ismounted eccentrically to first arm 102A in the embodiment of FIG. 7.Second fluke 106B is mounted eccentrically to second arm 102B and secondfluke 106B has a lateral extent that is larger than a lateral extent ofsecond arm 102B. First fluke 106A includes a first proximal surface 108Aprojecting at an outward angle in a proximal direction away from thedistal end of first arm 102A. Second fluke 106B includes a secondproximal surface 108B projecting at an outward angle in a proximaldirection away from the distal end of second arm 102B.

With reference to FIG. 7A, it will be appreciated that first fluke 106Aincludes a first point 120A and a first barb 122A. Second fluke 106Bincludes a second point 120B and a second barb 122B. The first barb 122Aand second barb 122B each have a cleft barb with two points and a valleythere between. In FIG. 7, first point 120A and second point 120B areshown generally pointing in the distal direction indicated by arrow D.Also in FIG. 7, first barb 122A and second barb 122B are shown generallypointing in the proximal direction indicated by arrow P.

With reference to FIG. 7A it will be appreciated that first fluke 106Adefines a first passageway 124A and second fluke 106B defines a secondpassageway 124B. In the exemplary embodiment of FIG. 7, first passageway124A extends through first fluke 106A and second passageway 124B extendsthrough second fluke 106B. It will be appreciated, however, that firstpassageway 124A may extend through other portions of staple 100 in someembodiments. Similarly, second passageway 124B may extend through otherportions of staple 100 in some embodiments. With reference to FIG. 7B itwill be appreciated that, first passageway 124A and second passageway124B each have a generally rectangular or square cross-sectional shape.It will be appreciated, however, that first passageway 124A and secondpassageway 124B may have various cross-sectional shapes withoutdeviating from the spirit and scope of the present detailed description.Further, each passageway can extend partially through the length of eachfluke rather than all the way through to provide a cavity rather than apassageway.

With reference to FIG. 7C, it will be appreciated that first barb 122Aof first fluke 106A defines a first notch 126A. In the exemplaryembodiment of FIG. 7, first notch 126A divides first barb 122A into afirst sub-barb and a second sub-barb. Second barb 122B of second fluke106B defines a second notch 126B. In the exemplary embodiment of FIG. 7,second notch 126B divides second barb 122B into a first sub-barb and asecond sub-barb. The barbs are thus clefted to form two points forgreater retention in tissue.

FIG. 8 is a perspective view showing staple 100 depicted in the previousFigure. Staple 100 comprises a first arm 102A, a second arm 102B, and abridge 104 extending from the proximal end of first arm 102A to theproximal end of second arm 102B. The distal end of first arm 102A abutsthe proximal end of a first fluke 106A.

With reference to FIG. 8 it will be appreciated that first fluke 106Adefines a first passageway 124A. In the exemplary embodiment of FIG. 8,first passageway 124A has a generally rectangular or squarecross-sectional shape. It will be appreciated, however, that firstpassageway 124A may have various cross-sectional shapes withoutdeviating from the spirit and scope of the present detailed description.

A second fluke 106B extends distally from second arm 102B with theproximal end of second fluke 106B abutting the distal end of second arm102B. With reference to FIG. 8, it will be appreciated that second fluke106B has a lateral extent that is larger than a lateral extent of secondarm 102B. Second fluke 106B is mounted eccentrically to second arm 102Bin the embodiment of FIG. 8. Similarly, first fluke 106A is mountedeccentrically to first arm 102A and first fluke 106A has a lateralextent that is larger than a lateral extent of first arm 102A.

A proximal direction is illustrated with an arrow P in FIG. 8. A distaldirection is illustrated with a second arrow D in FIG. 8. With referenceto FIG. 8A, it will be appreciated that first fluke 106A of first arm102A includes a first point 120A and a first barb 122A. Second fluke106B includes a second point 120B and a second barb 122B. In FIG. 8,first point 120A and second point 120B are shown generally pointing inthe distal direction indicated by arrow D. Also in FIG. 8, first barb122A and second barb 122B are shown generally pointing in the proximaldirection indicated by arrow P. With reference to FIG. 8, it will beappreciated that first fluke 106A includes a first proximal surface 108Aprojecting at an outward angle in a proximal direction away from thedistal end of first arm 102A. Second fluke 106B includes a secondproximal surface 108B projecting at an outward angle in a proximaldirection away from the distal end of second arm 102B.

FIG. 9 is a perspective view showing a staple push rod 130 that may beused in conjunction with staple 100 shown in the previous Figure. Staplepush rod 130 includes a shaft 132 and a pair of stakes 134 extendingdistally beyond a distal end of shaft 132. The distal direction isindicated with an arrow Din FIG. 9. Stakes 134 include a first stake134A and a second stake 134B. First stake 134A and second stake 134Bform a fork 136.

In the embodiment of FIG. 9, each stake 134 has a distal portion 138 anda proximal portion 140. In some useful embodiments, each distal portion138 is dimensioned to extend into a passage defined by a staple. In theembodiment of FIG. 9, each proximal portion 140 has a width larger thana width of each distal portion 138 so that a shoulder of each proximalportion 140 contacts a proximal surface of the staple to apply pushingforces thereto. First stake 134A comprises a first shoulder 142A andsecond stake 134B comprises a second shoulder 142B. Although depicted asa shoulder to provide pushing force to the staple, other designs can beutilized. For example, any larger cross section proximal portion canprovide a pushing force, such as a conical increase in profile. In theembodiment of FIG. 9, proximal portion 140 of first stake 134A and theproximal portion 140 of second stake 134B diverge from one another asthey extend in distal direction D away from shaft 132. In someapplications, this arrangement may cause pushing forces applied to twoflukes of a staple to have a laterally outward component.

In FIG. 9, first stake 134A and second stake 134B are shown assuming asubstantially unstressed state. It will be appreciated that first stake134A and second stake 134B can be resiliently urged to assume shapesother than the shape shown in FIG. 9. For example, first stake 134A andsecond stake 134B may be urged together so that fork 136 can be insertedinto a lumen having a diameter smaller than the distance between thedistal points of first stake 134A and second stake 134B shown in FIG. 9.

FIG. 10A and FIG. 10B illustrate multiple plan views of an exemplaryfixation tool 144 in accordance with the present detailed description.Fixation tool 144 incorporates staple push rod 130 and is useful indelivering staple 100. FIG. 10A and FIG. 10B may be referred tocollectively as FIG. 10. It is customary to refer to multi-viewprojections using terms such as front view, top view, and side view. Inaccordance with this convention, FIG. 10A may be referred to as a topview of fixation tool 144 and FIG. 10B may be referred to as a side viewof fixation tool 144. The terms top view and side view are used hereinas a convenient method for differentiating between the views shown inFIG. 10. It will be appreciated that the elements shown in FIG. 10 mayassume various orientations without deviating from the spirit and scopeof this detailed description. Accordingly, the terms top view and sideview should not be interpreted to limit the scope of the inventionrecited in the attached claims.

In the embodiment of FIG. 10, fixation tool 144 comprises a fixationtool shaft 146 that is attached to a handle 148. Fixation tool shaft 146comprises a wall 150 defining a lumen 152. With reference to FIG. 10, itwill be appreciated that fixation tool shaft 146 includes a first prong154A and a second prong 154B that extend distally beyond a distal end158 of lumen 152.

In FIG. 10, a staple 100 can be seen residing in lumen 152 of fixationtool shaft 146. For purposes of illustration, a distal portion offixation tool shaft 146 is enlarged in FIG. 10 to better show staple100. Staple 100 comprises a first arm 102A, a second arm 102B, and abridge 104 extending from the proximal end of first arm 102A to theproximal end of second arm 102B. The distal end of first arm 102A abutsthe proximal end of a first fluke 106A. Similarly, the distal end ofsecond arm 102B abuts the proximal end of a second fluke 106B. In FIG.10, first fluke 106A and second fluke 106B are shown extending distallyfrom first arm 102A and second arm 102B, respectively.

Staple push rod 130 includes a shaft 132 and a pair of stakes 134extending distally beyond a distal end of shaft 132. The distaldirection is indicated with an arrow D in FIG. 10. Stakes 134 include afirst stake 134A and a second stake 134B. In FIG. 10, a distal portionof each stake 134 extends into a passageway defined by staple 100. Inthe embodiment of FIG. 10, a trigger 160 is pivotably coupled to handle148 of fixation tool 144. Trigger 160 is operatively coupled to or incontact with staple push rod 130. In operation, staple push rod 130 willbe advanced and/or retracted in an axial direction when trigger 160 ispivoted relative to handle 148.

FIG. 11A is a further enlarged top view of a distal portion of fixationtool shaft 146 shown in the previous Figure. For purposes ofillustration, fixation tool shaft 146 is shown in partial cross-sectionin FIG. 11A so that staple 100 is visible residing in lumen 152. Withreference to FIG. 11A, it will be appreciated that staple 100 isdisposed on a distal portion of staple push rod 130. Staple 100comprises a first arm 102A, a second arm 102B, and a bridge 104extending from the proximal end of first arm 102A to the proximal end ofsecond arm 102B. The distal end of first arm 102A abuts the proximal endof a first fluke 106A. Similarly, the distal end of second arm 102Babuts the proximal end of a second fluke 106B. In FIG. 11, first fluke106A and second fluke 106B are shown extending distally from first arm102A and second arm 102B, respectively.

First fluke 106A and second fluke 106B define a first passageway 124Aand a second passageway 124B, respectively. In FIG. 11A, distal portion138 of first stake 134A of staple push rod 130 extends into firstpassageway 124A defined by first fluke 106A. A distal portion 138 ofsecond stake 134B of staple push rod 130 extends into a secondpassageway 124B defined by second fluke 106B of staple 100. In FIG. 11A,a first shoulder 142A of first stake 134A is shown contacting proximalsurface 108 of first fluke 106A. A second shoulder 142B of second stake134B is shown contacting proximal surface 108 of second fluke 106 inFIG. 11A. The distal portion 138 of first stake 134A extends distally offirst shoulder 142A and proximal portion 140 of first stake 134A extendsproximally of first shoulder 142A. The distal portion 138 of secondstake 134B extends distally of second shoulder 142B and a proximalportion 140 of second stake 134B extends proximally of second shoulder142B.

With reference to FIG. 11A, it will be appreciated that there is a gap Gbetween staple push rod 130 and bridge 104 of staple 100. In someapplications, gap G allows staple 100 to be placed in tension withoutbridge 104 contacting staple push rod 130. Staple 100 may be placed intension, for example, as staple 100 is advanced into a target tissue.

FIG. 11B is an additional top view showing a distal portion of fixationtool shaft 146, staple push rod 130, and staple 100. By comparing FIG.11A and FIG. 11B, it will be appreciated that staple push rod 130 andstaple 100 have been advanced in a distal direction D relative tofixation tool shaft 146. In FIG. 11B, staple 100 is shown extending outof lumen 152 defined by fixation tool shaft 146.

In FIG. 11B, a distal portion 138 of first stake 134A of staple push rod130 extends into a first passageway 124A defined by first fluke 106A ofstaple 100. In FIG. 11B, a first shoulder 142A of first stake 134A isshown contacting proximal surface 108 of first fluke 106A. Distalportion 138 of first stake 134A extends distally of first shoulder 142Aand proximal portion 140 of first stake 134A extends proximally of firstshoulder 142A. In some useful embodiments, the proximal portion of firststake 134A has a first width and the distal portion of first stake 134Ahas a second width different from the first width. In some particularlyuseful embodiments, the first width is greater than the first width. Thearrangement allows the proximal portion of stake to engage a proximalsurface of the staple to apply pushing forces to the staple.

In FIG. 11B, a distal portion 138 of second stake 134B of staple pushrod 130 extends into a second passageway 124B defined by second fluke106B of staple 100. In FIG. 11B, a second shoulder 142B of second stake134B is shown contacting proximal surface 108 of second fluke 106B. Inthe embodiment of FIG. 11B, proximal portion 140 of second stake 134Bmay apply pushing force to proximal surface 108 of second stake 134B.Proximal portion 140 of second stake 134B extends proximally of secondshoulder 142B and distal portion 138 of second stake 134B extendsdistally of second shoulder 142B. In the embodiment of FIG. 11B,proximal portion 140 of second stake 134B has a width larger than thewidth of distal portion 138 of second stake 134B so that the shoulder142 of second stake 134B contacts proximal surface 108 of second fluke106B to apply pushing forces thereto.

In the embodiment of FIG. 11B, first stake 134A and second stake 134Bare in a substantially unstressed state. It will be appreciated thatfirst stake 134A and second stake 134B can be resiliently urged toassume shapes other than the shape shown in FIG. 11. For example, firststake 134A and second stake 134B may be urged together so that fork 136of staple push rod 130 and staple 100 can be inserted into lumen 152defined by fixation tool shaft 146.

With reference to FIG. 11B, it will be appreciated that there is a gap Gbetween staple push rod 130 and bridge 104 of staple 100. In someapplications, gap G allows staple 100 to be placed in tension withoutbridge 104 contacting staple push rod 130. In some applications, placingstaple 100 under tension may urge first fluke 106 and second fluke 106into orientations which lock staple 100 into a target tissue. Forexample, first fluke 106A and second fluke 106B may be rotated so that abarb of each fluke engages the target tissue. When this is the case, thetension on the staple may keep first fluke 106A and second fluke 106B inthe rotated position. Also when this is the case, the barbs of therotated flukes may inhibit staple pullout.

FIG. 12A through FIG. 12C are a sequence of plan views illustrating anexemplary method in accordance with the present detailed description.FIG. 12A, FIG. 12B, and FIG. 12C may be collectively referred to as FIG.12. The exemplary method illustrated in FIG. 12 may be used, forexample, to fix a tendon repair implant 50 to a target tissue T using astaple 100.

At FIG. 12A, a fixation tool 144 has been used to form a first pilothole 162A and a second pilot hole 162B in target tissue T. In theembodiment of FIG. 12, fixation tool 144 includes a fixation tool shaft146 comprising a wall 150 defining a lumen 152. With reference to FIG.12, it will be appreciated that fixation tool shaft 146 includes a firstprong 154A and a second prong 154B that extend distally beyond a distalend 158 of lumen 152. In the embodiment of FIG. 12A, first prong 154Aand second prong 154B have been urged into tissue T to form first pilothole 162A and second pilot hole 162B. In FIG. 12A a distally directedforce F applied to fixation tool shaft 146 is illustrated using anarrow. Force F may be produced, for example, by pushing on a handle thatis fixed to a proximal portion of fixation tool shaft 146. It will beappreciated that in some embodiments, such as the embodiment depicted inFIG. 6, one of the first and second pilot holes may be formed throughthe sheet-like implant and the target tissue, and the other pilot holemay be formed directly in the target tissue without passing through thesheet-like implant. In other words, in various embodiments staples maystraddle the perimeter edge of the sheet-like implant (as shown in FIG.6), may be applied adjacent to the perimeter, and/or be applied to acentral region of the implant. In some embodiments, the staples may beused to attach the implant to soft tissue and/or to bone. In FIG. 12A, astaple 100 can be seen residing in lumen 152 of fixation tool shaft 146.For purposes of illustration, fixation tool shaft 146 is shown inpartial cross-section in FIG. 12A so that staple 100 is visible residingin lumen 152. With reference to FIG. 12, it will be appreciated thatstaple 100 is carried by a fork 136 comprising a first stake 134A and asecond stake 134B. In FIG. 12A, a distal portion of first stake 134A ofstaple push rod 130 extends into a first passageway defined by firstfluke 106A. A distal portion of second stake 134B of staple push rod 130extends into a second passageway defined by second fluke 106B of staple100.

In some useful embodiments, each stake is positioned relative to a prongalong an inner surface of fixation tool shaft 146 so that the stakesadvance into the pilot holes when the stakes are moved in a distaldirection. Staple push rod 130 is slidably disposed within lumen 152defined by fixation tool shaft 146. Fixation tool 144 includes amechanism that is capable of creating relative axial motion betweenstaple push rod 130 and fixation tool shaft 146 so that staple push rod130 slides along fixation tool shaft 146.

At FIG. 12B, relative motion has been created between staple push rod130 and fixation tool shaft 146 while distally directed force F has beencontinuously applied to fixation tool shaft 146. By comparing FIG. 12Band FIG. 12A, it will be appreciated that first stake 134A and secondstake 134B have been advanced in a distal direction D. With reference toFIG. 12, it will also be appreciated that first stake 134A and secondstake 134B have advanced into first pilot hole 162A and second pilothole 162B, respectively. In FIG. 12B, first fluke 106A is shown residingin first pilot hole 162. Second fluke 106B is residing in second pilothole 162 in the embodiment of FIG. 12B.

At FIG. 12C, additional relative motion has been created between staplepush rod 130 and fixation tool shaft 146 while distally directed force Fhas been continuously applied to fixation tool shaft 146. By comparingFIG. 12C and FIG. 12B, it will be appreciated that the relative motionbetween staple push rod 130 and fixation tool shaft 146 has movedfixation tool shaft 146 in a proximal direction P.

By comparing FIG. 12C and FIG. 12B, it will also be appreciated thatfirst arm 102A of staple 100 has been bent and first fluke 106A has beenrotated to a toggled position. In the exemplary embodiment of FIG. 12C,force applied to first fluke 106A by first shoulder 142A has causedfirst fluke 106A to rotate. With continuing reference to FIG. 12C andFIG. 12B, it will be appreciated that second arm 102B of staple 100 hasbeen bent and second fluke 106A has been rotated to a toggled position.In the exemplary embodiment of FIG. 12C, force applied to second fluke106 b by second shoulder 142B has caused second fluke 106B to rotate.

With reference to FIG. 12C, it will be appreciated that a first throughhole 164A and a second through hole 164B have been formed in tendonrepair implant 50. In the embodiment of FIG. 12, first through hole 164Aand a second through hole 164B were created by urging first prong 154Aand second prong 154B of fixation tool shaft 146 through tendon repairimplant 50.

FIG. 13A, FIG. 13B, and FIG. 13C are multiview projections illustratinga fixation tool shaft 146 shown in the previous Figures. FIG. 13D is across-sectional view of fixation tool shaft 146 sectioned along cuttingplane D-D illustrated in FIG. 13C. These Figures may be collectivelyreferred to as FIG. 13. Fixation tool shaft 146 of FIG. 13 comprises awall 150 defining a lumen 152. A first prong 154A and a second prong154B of fixation tool shaft 146 extend distally beyond a distal end 158of lumen 152.

With reference to FIG. 13, it will be appreciated that fixation toolshaft 146 comprises a proximal portion 170, a distal portion 168 and anintermediate portion 166 disposed between proximal portion 170 anddistal portion 168. In the embodiment of FIG. 13, distal portion 168 hasan axial extent DA, a major lateral extent LA and a minor lateral extentLB. With reference to FIG. 13, it will be appreciated that axial extentDA is greater than both minor lateral extent LB and major lateral extentLA.

FIG. 14 is an enlarged axial view of fixation tool shaft 146 shown inthe previous Figure. With reference to FIG. 14, it will be appreciatedthat proximal portion 170 of fixation tool shaft 146 comprises a wall150 having an outer surface 172. In FIG. 14, outer surface 172 isillustrated using a circle. Thus, it will be appreciated that proximalportion 170 of fixation tool shaft 146 has a generally cylindrical outershape in the exemplary embodiment of FIG. 14. In the exemplaryembodiment of FIG. 14, fixation tool shaft 146 has a generally uniformwall thickness. Accordingly, the shape of proximal portion 170 may begenerally described as a cylindrical tube. The shape of distal portion168 may be described as a cylindrical-tube that has been partiallyflattened. In the exemplary embodiment of FIG. 14, distal portion 168 offixation tool shaft 146 has a major lateral extent LA and a minorlateral extent LB. With reference to FIG. 14, it will be appreciatedthat major lateral extent LA is greater than minor lateral extent LB.

FIG. 15 is an additional enlarged axial view of fixation tool shaft 146.With reference to FIG. 15, it will be appreciated that distal portion168 of fixation tool shaft 146 comprises a first major side SA, a secondmajor side SB, a first minor side SC, and a second minor side SD. In theexemplary embodiment of FIG. 15, each minor side has a first centralradius RA and each major side has a second central radius RB. Withreference to FIG. 15, it will be appreciated that second central radiusRB is greater than first central radius RA. In the exemplary embodimentof FIG. 15, first major side SA, second major side SB, first minor sideSC, and second minor side SD each have a generally convex shape. In theexemplary embodiment of FIG. 15, each minor side is generally moreconvex than each major side.

FIG. 16 is an exploded isometric view showing an exemplary fixation tool144 in accordance with this detailed description. In the embodiment ofFIG. 16, fixation tool 144 comprises a fixation tool shaft 146 and ahandle 144. In FIG. 16, handle 148 is exploded into two pieces. Aproximal portion of fixation tool shaft 146 is fixed to handle 148 whenfixation tool 144 is in an assembled state. Fixation tool 144 alsocomprises a staple push rod 130. A distal portion of staple push rod 130extends into a lumen 152 of fixation tool shaft 146 when fixation tool144 is in the assembled state.

Fixation tool shaft 146 comprises a wall 150 defining a lumen 152. Withreference to FIG. 16, it will be appreciated that fixation tool shaft146 includes a first prong 154A and a second prong 154B that extenddistally beyond a distal end 158 of lumen 152. In some usefulembodiments, first prong 154A and second prong 154B form pilot holes ina target tissue when the distal portion of fixation tool shaft 146 ispressed against the target tissue.

A staple 100 of fixation tool 144 is carried by a fork 136 in theembodiment of FIG. 16, as with prior embodiments. A fluke of staple 100may be advanced into each pilot hole formed by the prongs of fixationtool shaft 146. Fork 136 of fixation tool 144 comprises a first stake134A and a second stake 134B. First stake 134A and second stake 134B arefixed to a distal end of a staple push rod 130 in the embodiment of FIG.16.

Staple push rod 130 includes a first tubular member 182, a secondtubular member 184 and a force limiting mechanism 186 operably coupledbetween first tubular member 182 and second tubular member 184. Theproximal end of first tubular member 182 is coupled to a lever 174.Lever 174 is coupled to a trigger 160. Trigger 160 is pivotablysupported by handle 148 of fixation tool 144 when fixation tool 144 isin an assembled state. Trigger 160 and lever 174 form part of anactuator assembly 176 that is capable of creating longitudinal movementof first tubular member 182 of staple push rod 130 relative to fixationtool shaft 146. In operation, first tubular member 182 of staple pushrod 130 will be advanced and/or retracted in an axial direction whentrigger 160 is pivoted relative to handle 148. In some cases, the motionproduced by actuator assembly 176 is transferred to staple 100 carriedby fork 136.

Actuator assembly 176 may be used to control the motion of first tubularmember 182. In the embodiment of FIG. 16, force limiting mechanism 186will transmit longitudinal movement between first tubular member 182 andsecond tubular member 184 as long as the forces applied to staple 100 bystaple push rod 130 are less than a predetermined value. If the forcesapplied to staple 100 are equal to or greater than the predeterminedvalue, then force limiting mechanism 186 will allow relativelongitudinal motion between first tubular member 182 and second tubularmember 184. In some useful embodiments, this function of force limitingmechanism 186 prevents the application of undue forces to staple 100.Once the force applied to staple 100 reaches a pre-selected threshold,further rotation of trigger 160 will result in relative motion betweenfirst tubular member 182 and second tubular member 184 and will notresult in the application of additional force to staple 100. Forcelimiting mechanism 186 is represented by a block in FIG. 16 and maycomprise various force limiting arrangements without deviating from thespirit and scope of this detailed description.

FIG. 17 is a perspective view showing an illustrative fixation toolassembly 181 in accordance with this detailed description. In theembodiment of FIG. 17, fixation tool assembly 181 comprises a staplepush rod 130 and a fixation tool shaft 146. A distal portion of staplepush rod 130 extends into a lumen 152 defined by fixation tool shaft 146when fixation tool assembly 181 is in an assembled state. Staple pushrod 130 includes a first tubular member 182, a second tubular member 184and a force limiting mechanism 186 operably coupled between firsttubular member 182 and second tubular member 184.

In the exemplary embodiment of FIG. 17, a distal portion of firsttubular member 182 is slidingly received in a lumen defined by secondtubular member 184 such that first tubular member 182 and second tubularmember 184 can translate relative to each other. Second tubular member184 defines a slot 194. First tubular member 182 carries a pin 196 thatis slidingly received in slot 194 such that relative rotation betweenfirst tubular member 182 and second tubular member 184 is prevented.

An actuator assembly 176 is coupled to the proximal end of first tubularmember 182. Actuator assembly 176 is capable of creating longitudinalmovement of first tubular member 182 of staple push rod 130 relative tofixation tool shaft 146. In the embodiment of FIG. 17, actuator assembly176 comprises a lever 174 and a trigger 160. Lever 174 is pivotablycoupled to a proximal end of first tubular member 182. Trigger 160engages lever 174 such that rotation of trigger 160 causes rotation oflever 174.

In operation, first tubular member 182 of staple push rod 130 will beadvanced and/or retracted in a longitudinal direction when trigger 160and lever 174 are rotated. Under certain circumstances, the longitudinalmotion of first tubular member 182 is transferred to second tubularmember 184 by force limiting mechanism 186. When certain conditions aremet, however, force limiting mechanism 186 does not transfer thelongitudinal motion of first tubular member 182 to second tubular member184.

A staple 100 is disposed at a distal end of second tubular member 184.In the embodiment of FIG. 17, force limiting mechanism 186 will transmitthe longitudinal movement of first tubular member 182 to second tubularmember 184 as long as the forces applied to staple 100 by staple pushrod 130 are less than a predetermined value. Accordingly, longitudinalmovement of first tubular member 182 of staple push rod 130 will causesubstantially equivalent longitudinal movement of second tubular member184 as long as the forces applied to staple 100 by staple push rod 130are less than the predetermined value. If the forces applied to staple100 are equal to or greater than the predetermined value, then forcelimiting mechanism 186 will allow relative longitudinal motion betweenfirst tubular member 182 and second tubular member 184. In some usefulembodiments, this function of force limiting mechanism 186 prevents theapplication of undue forces to staple 100. Once the maximum desiredforce is applied to staple 100, further rotation of trigger 160 willresult in relative motion between first tubular member 182 and secondtubular member 184 and will not result in the application of additionalforce to staple 100.

In the embodiment of FIG. 17, force limiting mechanism 186 comprises aspring 188. A first end of spring 188 is pivotably coupled to firsttubular member 182 at a first joint 190A. A second end of spring 188 ispivotably coupled to second tubular 184 member at a second joint 190B.In some particularly useful embodiments, spring 188 comprises a constantforce spring. Spring 188 may comprise various constant force springswithout deviating form the spirit and scope of the present invention.One constant force spring that may be suitable in some applications isdisclosed in U.S. Pat. No. 2,630,316. With reference to FIG. 17 it willbe appreciated that spring 188 comprises a plurality of wire turnsarranged to extend along a longitudinal axis 198. With reference of toFIG. 17, it will be appreciated that the wire turns of spring 188 arearranged so that spring 188 extends along a straight longitudinal axisin the illustrated embodiment. Spring 188 will maintain the straightshape shown in FIG. 17 as long as the forces applied to staple 100 bystaple push rod 130 are less than a predetermined value. In operation,spring 188 will transmit the longitudinal movement of first tubularmember 182 to second tubular member 184 as long as the forces applied tostaple 100 by staple push rod 130 are less than the predetermined value.If the forces applied to staple 100 are equal to or greater than thepredetermined value, then spring 188 will bend such that the wire turnsof spring 188 extend along a curvilinear longitudinal axis. When spring188 bends, spring 188 allows relative longitudinal motion between firsttubular member 182 and second tubular member 184.

With reference to FIG. 17, it will be appreciated that staple 100 iscarried by a pair of stakes 134 that extend distally beyond a distal endof second tubular member 184. The distal direction is indicated with anarrow D in FIG. 17. Stakes 134 include a first stake 134A and a secondstake 134B. In FIG. 17, a distal portion of each stake 134 extends intoa passageway defined by staple 100. Staple 100 comprises a first arm, asecond arm, and a bridge 104 extending from the proximal end of thefirst arm to the proximal end of the second arm. The distal end of thefirst arm abuts the proximal end of a first fluke 106A of staple 100.Similarly, the distal end of the second arm abuts the proximal end of asecond fluke 106B.

In the embodiment of FIG. 17, a distal portion of first stake 134Aextends into a first passageway defined by first fluke 106A. Similarly,a distal portion of second stake 134B extends into a second passagewaydefined by second fluke 106B of staple 100. A first shoulder of firststake 134A contacts a proximal surface of first fluke 106A in theembodiment of FIG. 17. A second shoulder of second stake 134B contacts aproximal surface of second fluke 106B.

Fixation tool shaft 146 of FIG. 17 comprises a wall 150 defining a lumen152. With reference to FIG. 17, it will be appreciated that fixationtool shaft 146 includes a first prong 154A and a second prong 154B thatextend distally beyond a distal end 158 of lumen 152. In some usefulembodiments, first prong 154A and second prong 154B form pilot holes ina target tissue when the distal portion of fixation tool shaft 146 ispressed against the target tissue. A fluke of staple 100 may be advancedinto each pilot hole formed by the prongs of fixation tool shaft 146.

FIG. 18A and FIG. 18B are plan views further illustrating the operationof fixation tool assembly 181 shown in the previous figure. FIG. 18A andFIG. 18B may be collectively referred to as FIG. 18. Fixation toolassembly 181 comprises a staple push rod 130 including a first tubularmember 182, a second tubular member 184 and a force limiting mechanism186 operably coupled between first tubular member 182 and second tubularmember 184. In the exemplary embodiment of FIG. 18, a distal portion offirst tubular member 182 is slidingly received in a lumen defined bysecond tubular member 184 such that first tubular member 182 and secondtubular member 184 can translate relative to each other.

An actuator assembly 176 including a lever 174 is coupled to theproximal end of first tubular member 182. Actuator assembly 176 iscapable of creating longitudinal movement of first tubular member 182 ofstaple push rod 130. In operation, first tubular member 182 of staplepush rod 130 will be advanced and/or retracted in a longitudinaldirection when lever 174 of actuator assembly 176 is rotated. Undercertain circumstances, the longitudinal motion of first tubular member182 is transferred to second tubular member 184 by force limitingmechanism 186. When certain conditions are met, however, force limitingmechanism 186 does not transfer the longitudinal motion of first tubularmember 182 to second tubular member 184.

A staple 100 is disposed at a distal end of second tubular member 184.In the embodiment of FIG. 18, force limiting mechanism 186 will transmitthe longitudinal movement of first tubular member 182 to second tubularmember 184 as long as the forces applied to staple 100 by staple pushrod 130 are less than a predetermined value. Accordingly, longitudinalmovement of first tubular member 182 of staple push rod 130 will causesubstantially equivalent longitudinal movement of second tubular member184 as long as the forces applied to staple 100 by staple push rod 130are less than the predetermined value. If the forces applied to staple100 are equal to or greater than the predetermined value, then forcelimiting mechanism 186 will allow relative longitudinal motion betweenfirst tubular member 182 and second tubular member 184. In some usefulembodiments, this function of force limiting mechanism 186 prevents theapplication of undue forces to staple 100. Once the maximum desiredforce is applied to staple 100, further rotation of lever 174 willresult in relative motion between first tubular member 182 and secondtubular member 184 and will not result in the application of additionalforce to staple 100.

In the embodiment of FIG. 18, force limiting mechanism 186 comprises aspring 188. A first end of spring 188 is pivotably coupled to firsttubular member 182 at a first joint 190A. A second end of spring 188 ispivotably coupled to second tubular 184 member at a second joint 190B.In some particularly useful embodiments, spring 188 comprises a constantforce spring. Spring 188 may comprise various constant force springswithout deviating form the spirit and scope of the present invention.One constant force spring that may be suitable in some applications isdisclosed in U.S. Pat. No. 2,630,316. With reference to FIG. 18 is willbe appreciated that spring 188 comprises a plurality of wire turnsarranged to extend along a longitudinal axis 198.

In the embodiment of FIG. 18A, the wire turns of spring 188 are arrangedso that spring 188 extends along a straight longitudinal axis. Spring188 will maintain the straight shape shown in FIG. 18A as long as theforces applied to staple 100 by staple push rod 130 are less than apredetermined value. In operation, spring 188 will transmit thelongitudinal movement of first tubular member 182 to second tubularmember 184 as long as the forces applied to staple 100 by staple pushrod 130 are less than a predetermined value.

In the embodiment of FIG. 18B, spring 188 is bent so that the wire turnsof spring 188 are arranged with spring 188 extending along a curvilinearlongitudinal axis. If the forces applied to staple 100 are equal to orgreater than the predetermined value, then spring 188 will bend suchthat the wire turns of spring 188 extend along a curvilinearlongitudinal axis. The resistance to additional bending offered byspring 300 remains substantially constant as spring 300 is bent from theshape shown in FIG. 18A to the shape shown in FIG. 18B. When spring 188bends, spring 188 allows relative longitudinal motion between firsttubular member 182 and second tubular member 184. Dimension lines areused to illustrate an overall length LA and an overall length LB in FIG.18A and FIG. 18B, respectively. With reference to FIG. 18, it will beappreciated that overall length LB is shorter than overall length LA. Inthe embodiment of FIG. 18, the difference between overall length LB andoverall length LA is due to relative longitudinal motion between firsttubular member 182 and second tubular member 184.

FIG. 19 is a perspective view showing an illustrative fixation toolassembly 180 in accordance with this detailed description. In theembodiment of FIG. 19, fixation tool assembly 180 comprises a staplepush rod 130 and a fixation tool shaft 146. A distal portion of staplepush rod 130 extends into a lumen 152 defined by fixation tool shaft 146when fixation tool assembly is in an assembled state. Staple push rod130 includes a first tubular member 182, a second tubular member 184 anda force limiting mechanism 186 operably coupled between first tubularmember 182 and second tubular member 184. A staple 100 is disposed atthe distal end of second tubular member 184 and a lever 174 is connectedto the proximal end of first tubular member 182.

Staple 100 is carried by a fork 136 that extends distally beyond thedistal end of second tubular member 184. The distal direction isindicated with an arrow D in FIG. 19. Fork 136 includes a first stake134A and a second stake 134B. In FIG. 19, a distal portion of each stakeextends into a passageway defined by staple 100. Staple 100 comprises afirst arm, a second arm, and a bridge 104 extending from the proximalend of the first arm to the proximal end of the second arm. The distalend of the first arm abuts the proximal end of a first fluke 106A ofstaple 100. Similarly, the distal end of the second arm abuts theproximal end of a second fluke 106B.

In the embodiment of FIG. 19, a distal portion of first stake 134Aextends into a first passageway defined by first fluke 106A. Similarly,a distal portion of second stake 134B extends into a second passagewaydefined by second fluke 106B of staple 100. A first shoulder of firststake 134A contacts a proximal surface of first fluke 106A in theembodiment of FIG. 19. A second shoulder of second stake 134B contacts aproximal surface of second fluke 106B.

Fixation tool shaft 146 of FIG. 19 comprises a wall 150 defining a lumen152. With reference to FIG. 19, it will be appreciated that fixationtool shaft 146 includes a first prong 154A and a second prong 154B thatextend distally beyond a distal end 158 of lumen 152. In some usefulembodiments, first prong 154A and second prong 154B form pilot holes ina target tissue when the distal portion of fixation tool shaft 146 ispressed against the target tissue. A fluke of staple 100 may be advancedinto each pilot hole formed by the prongs of fixation tool shaft 146.

An actuator assembly 176 is operably coupled to first tubular member 182of staple push rod 130. Actuator assembly 176 is capable of moving firsttubular member 182 in a longitudinal direction relative to fixation toolshaft 146. In the embodiment of FIG. 19, actuator assembly 176 comprisesa lever 174 and a trigger 160. With reference to FIG. 19, it will beappreciated that lever 174 is pivotably coupled to the proximal end offirst tubular member 182. Trigger 160 engages lever 174 in such a waythat rotation of trigger 160 causes rotation of lever 174. In operation,first tubular member 182 of staple push rod 130 will be advanced and/orretracted in a longitudinal direction when trigger 160 and lever 174 arerotated.

In the embodiment of FIG. 19, force limiting mechanism 186 will transmitthe longitudinal movement of first tubular member 182 to second tubularmember 184 as long as the forces applied to staple 100 by staple pushrod 130 are less than a predetermined value. Accordingly, longitudinalmovement of first tubular member 182 of staple push rod 130 will causesubstantially equivalent longitudinal movement of second tubular member184 as long as the forces applied to staple 100 by staple push rod 130are less than the predetermined value. If the forces applied to staple100 are equal to or greater than the predetermined value, then forcelimiting mechanism 186 will allow relative longitudinal motion betweenfirst tubular member 182 and second tubular member 184. In some usefulembodiments, this function of force limiting mechanism 186 prevents theapplication of undue forces to staple 100. Once the maximum desiredforce is applied to staple 100, further rotation of trigger 160 willresult in relative motion between first tubular member 182 and secondtubular member 184 and will not result in the application of additionalforce to staple 100.

In the embodiment of FIG. 19, force limiting mechanism 186 comprises aspring 300. Spring 300 of FIG. 19, comprises ribbon 312 that forms aroll 314 when ribbon 312 is in an unstressed state. When fixation toolassembly 180 is in an assembled state, roll 314 is supported by a roller316 that extends through a center opening of roll 314. Roller 316 isrotatably supported by a bracket that is fixed to second tubular member184 when fixation tool assembly 180 is in an assembled state. Secondtubular member 184 defines a slot 194. First tubular member 182 carriesa pin 196 that extends through slot 194. When fixation tool assembly 180is in an assembled state, free end 318 of spring 300 is affixed to pin196. In the embodiment of FIG. 19, the arrangement of pin 196 extendingthrough slot 194 prevents relative rotation between first tubular member182 and second tubular member 184.

When spring 300 is in an unstressed state, ribbon 312 forms a roll 314as illustrated in FIG. 19. Spring 300 will maintain the rolled shapeshown in FIG. 19 as long as the forces applied to staple 100 by staplepush rod 130 are less than a predetermined value. In operation, spring300 will transmit the longitudinal movement of first tubular member 182to second tubular member 184 as long as the forces applied to staple 100by staple push rod 130 are less than a predetermined value. If theforces applied to staple 100 are equal to or greater than thepredetermined value, then spring 300 will unroll. When spring 300unrolls, spring 300 allows relative longitudinal motion between firsttubular member 182 and second tubular member 184. As ribbon 312 of roll314 is unrolled, the force produced by spring 300 comes primarily fromthe portion of ribbon 312 near roll 314. Because the geometry of thatregion remains nearly constant as ribbon 312 unrolls, the resultingforce is nearly constant.

FIG. 20A and FIG. 20B are plan views further illustrating the operationof fixation tool assembly 180 shown in the previous figure. FIG. 20A andFIG. 20B may be collectively referred to as FIG. 20. Fixation toolassembly 180 comprises a staple push rod 130 including a first tubularmember 182, a second tubular member 184 and a force limiting mechanism186 operably coupled between first tubular member 182 and second tubularmember 184. In the exemplary embodiment of FIG. 20, a distal portion offirst tubular member 182 is slidingly received in a lumen defined bysecond tubular member 184 such that first tubular member 182 and secondtubular member 184 can translate relative to each other.

An actuator assembly 176 including a lever 174 is coupled to theproximal end of first tubular member 182. Actuator assembly 176 iscapable of creating longitudinal movement of first tubular member 182 ofstaple push rod 130 relative to fixation tool shaft 146. In operation,first tubular member 182 of staple push rod 130 will be advanced and/orretracted in a longitudinal direction when lever 174 of actuatorassembly 176 is rotated. Under certain circumstances, the longitudinalmotion of first tubular member 182 is transferred to second tubularmember 184 by force limiting mechanism 186. When certain conditions aremet, however, force limiting mechanism 186 does not transfer thelongitudinal motion of first tubular member 182 to second tubular member184.

A staple 100 is disposed at a distal end of second tubular member 184.In the embodiment of FIG. 20, force limiting mechanism 186 will transmitthe longitudinal movement of first tubular member 182 to second tubularmember 184 as long as the forces applied to staple 100 by staple pushrod 130 are less than a predetermined value.

Accordingly, longitudinal movement of first tubular member 182 of staplepush rod 130 will cause substantially equivalent longitudinal movementof second tubular member 184 as long as the forces applied to staple 100by staple push rod 130 are less than the predetermined value. If theforces applied to staple 100 are equal to or greater than thepredetermined value, then force limiting mechanism 186 will allowrelative longitudinal motion between first tubular member 182 and secondtubular member 184. In some useful embodiments, this function of forcelimiting mechanism 186 prevents the application of undue forces tostaple 100. Once the maximum desired force is applied to staple 100,further rotation of lever 174 will result in relative motion betweenfirst tubular member 182 and second tubular member 184 and will notresult in the application of additional force to staple 100.

In the embodiment of FIG. 20, force limiting mechanism 186 comprises aspring 300. Spring 300 of FIG. 20, comprises ribbon 312 that forms aroll 314 when ribbon 312 is in an unstressed state. When fixation toolassembly 180 is in an assembled state, roll 314 is supported by a roller316 that extends through a center opening of roll 314. Roller 316 isrotatably supported by a bracket that is fixed to second tubular member184. First tubular member 182 carries a pin 196 that extends through aslot defined by second tubular member 184. Free end 318 of spring 300 isaffixed to pin 196 in the embodiment of FIG. 20.

When spring 300 is in an unstressed state, ribbon 312 forms a roll 314as illustrated in FIG. 20A. Spring 300 will maintain the rolled shapeshown in FIG. 20A as long as the forces applied to staple 100 by staplepush rod 130 are less than a predetermined value. In operation, spring300 will transmit the longitudinal movement of first tubular member 182to second tubular member 184 as long as the forces applied to staple 100by staple push rod 130 are less than a predetermined value. If theforces applied to staple 100 are equal to or greater than thepredetermined value, then spring 300 will umoll. When spring 300 umolls,spring 300 allows relative longitudinal motion between first tubularmember 182 and second tubular member 184. In the embodiment of FIG. 20B,spring 300 has been partially umolled relative to the unstressed stateof spring 300. Dimension lines are used to illustrate an overall lengthLA and an overall length LB in FIG. 20A and FIG. 20B, respectively. Withreference to FIG. 20, it will be appreciated that overall length LB isshorter than overall length LA. In the embodiment of FIG. 20, thedifference between overall length LB and overall length LA is due torelative longitudinal motion between first tubular member 182 and secondtubular member 184. As ribbon 312 of roll 314 is unrolled, the forceproduced by spring 300 comes primarily from the portion of ribbon 312near roll 314. Because the geometry of that region remains nearlyconstant as ribbon 312 unrolls, the resulting force is nearly constant.

While exemplary embodiments of the present invention have been shown anddescribed, modifications may be made, and it is therefore intended inthe appended claims and subsequently filed claims to cover all suchchanges and modifications which fall within the true spirit and scope ofthe invention.

What is claimed is:
 1. A device for attaching a sheet-like implant to atarget tissue, comprising: a sheath having a proximal end and a distalend; a fastener push rod disposed at least partially within the sheath,the fastener push rod including a first portion and a second portion;and an actuator assembly coupled to the fastener push rod first portionand capable of applying a force to the fastener push rod first portion,wherein the fastener push rod first portion is coupled to the fastenerpush rod second portion such that when the force applied to the fastenerpush rod first portion is below a force threshold, the fastener push rodfirst portion translates the applied force to the fastener push rodsecond portion, and wherein if the force applied to the fastener pushrod first portion is above the force threshold, the fastener push rodfirst portion and the fastener push rod second portion move relative toeach other so that a force above the force threshold is not translatedto the fastener push rod second portion.
 2. The device of claim 1,wherein, if the force applied to the fastener push rod first portion isabove the force threshold, a force that is equal to or below the forcethreshold is still translated to the fastener push rod second portion 3.The device of claim 1, further comprising a force limiting mechanismcoupling the push rod first portion to the push rod second portion. 4.The device of claim 3, wherein the force limiting mechanism comprises aconstant force spring, a first end of the constant force spring beingcoupled to the fastener push rod first portion, and a second end of theconstant force spring being coupled to the fastener push rod secondportion.
 5. The device of claim 1, wherein the first portion of thefastener push rod includes a first tubular member, the second portion ofthe fastener push rod includes a second tubular member, and a portion ofone of the first tubular member and the second tubular member isslidingly received in a lumen defined by the other of the first tubularmember and the second tubular member such that the first tubular memberand the second tubular member can translate relative to each other. 6.The device of claim 5, wherein when a force above the force threshold isapplied to the push rod first portion, the push rod first portion andthe push rod second portion translate relative to each other.
 7. Thedevice of claim 5, wherein one of the first tubular member and thesecond tubular member defines a slot, and the other of the first tubularmember and the second tubular member carries a pin that is slidinglyreceived in the slot such that relative rotation between the firsttubular member and the second tubular member is prevented.
 8. The deviceof claim 1, wherein the sheath comprises a plurality of prongs disposedproximate the distal end of the sheath, the prongs configured forforming pilot holes when pushed against the target tissue.
 9. A devicefor attaching a sheet-like implant to a target tissue, comprising: afastener push rod including a first portion and a second portion; anactuator assembly coupled to the first portion of the fastener push rod,wherein movement of the actuator assembly translates a force to thefastener push rod first portion; and a relative motion coupling betweenthe fastener push rod first portion and the fastener push rod secondportion, wherein the relative motion coupling allows relative motionbetween the fastener push rod first portion and the fastener push rodsecond portion when a force applied to the fastener push rod firstportion exceeds a predetermined amount of force.
 10. The device of claim9, wherein the relative motion coupling restricts relative motionbetween the push rod first portion and the push rod second portion whena force applied to the fastener push rod first portion is equal to orless than the predetermined amount of force.
 11. The device of claim 10,wherein the relative motion coupling restricts relative motion only inone direction between the fastener push rod first portion and thefastener push rod second portion when a force applied to the fastenerpush rod first portion is equal to or less than the predetermined amountof force.
 12. The device of claim 9, wherein the relative motioncoupling comprises a constant force spring, a first end of the constantforce spring being coupled to the fastener push rod first portion, and asecond end of the constant force spring being coupled to the fastenerpush rod second portion.
 13. The device of claim 9, wherein the firstportion of the fastener push rod includes a first tubular member, thesecond portion of the fastener push rod includes a second tubularmember, and a portion of one of the first tubular member and the secondtubular member is slidingly received in a lumen defined by the other ofthe first tubular member and the second tubular member such that thefirst tubular member and the second tubular member can translaterelative to each other.
 14. The device of claim 13, wherein one of thefirst tubular member and the second tubular member defines a slot, andthe other of the first tubular member and the second tubular membercarries a pin that is slidingly received in the slot such that relativerotation between the first tubular member and the second tubular memberis prevented.
 15. An apparatus for delivering staples to a targettissue, the apparatus comprising: a sheath having a proximal end and adistal end; a fastener push rod disposed at least partially within thesheath and translatable relative to the sheath, the fastener push rodincluding a first portion and a second portion; a fastener disposed onthe fastener push rod second portion; and a coupler coupling thefastener push rod first portion and the fastener push rod secondportion, wherein the coupler translates forces on the fastener push rodfirst portion to the fastener push rod second portion when the forcesare below a force threshold, and wherein the coupler does not translateforces on the fastener push rod first portion to the fastener push rodsecond portion when the forces are above the force threshold.
 16. Theapparatus of claim 15, wherein the coupler allows relative movementbetween the fastener push rod first portion and the fastener push rodsecond portion when forces on the fastener push rod first portion exceedthe force threshold.
 17. The apparatus of claim 16, wherein the couplerrestricts relative movement between the fastener push rod first portionand the fastener push rod second portion when the forces on the fastenerpush rod first portion are equal to or less than the force threshold.18. The apparatus of claim 15, wherein the coupler has a firstlongitudinal extent when the forces on the push rod first portion areequal to or less than the force threshold and the coupler has a second,smaller longitudinal extent when the forces on the push rod firstportion are greater than the force threshold.
 19. The apparatus of claim15, wherein the coupler comprises a constant force spring, a first endof the constant force spring being coupled to the fastener push rodfirst portion, and a second end of the constant force spring beingcoupled to the fastener push rod second portion.
 20. The apparatus ofclaim 15, wherein the first portion of the fastener push rod includes afirst tubular member, the second portion of the fastener push rodincludes a second tubular member, and a portion of one of the firsttubular member and the second tubular member is slidingly received in alumen defined by the other of the first tubular member and the secondtubular member such that the first tubular member and the second tubularmember can translate relative to each other.